800 research outputs found

    Advanced extravehicular activity systems requirements definition study. Phase 2: Extravehicular activity at a lunar base

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    The focus is on Extravehicular Activity (EVA) systems requirements definition for an advanced space mission: remote-from-main base EVA on the Moon. The lunar environment, biomedical considerations, appropriate hardware design criteria, hardware and interface requirements, and key technical issues for advanced lunar EVA were examined. Six remote EVA scenarios (three nominal operations and three contingency situations) were developed in considerable detail

    A Signature of Inflation from Dynamical Supersymmetry Breaking

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    In models of cosmological inflation motivated by dynamical supersymmetry breaking, the potential driving inflation may be characterized by inverse powers of a scalar field. These models produce observables similar to those typical of the hybrid inflation scenario: negligible production of tensor (gravitational wave) modes, and a blue scalar spectral index. In this short note, we show that, unlike standard hybrid inflation models, dynamical supersymmetric inflation (DSI) predicts a measurable deviation from a power-law spectrum of fluctuations, with a variation in the scalar spectral index dn/d(lnk)|dn / d(\ln k)| may be as large as 0.05. DSI can be observationally distinguished from other hybrid models with cosmic microwave background measurements of the planned sensitivity of the ESA's Planck Surveyor.Comment: LaTeX file, 9 pages, 1 fig.ep

    International cooperation for Mars exploration and sample return

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    The National Research Council's Space Studies Board has previously recommended that the next major phase of Mars exploration for the United States involve detailed in situ investigations of the surface of Mars and the return to earth for laboratory analysis of selected Martian surface samples. More recently, the European space science community has expressed general interest in the concept of cooperative Mars exploration and sample return. The USSR has now announced plans for a program of Mars exploration incorporating international cooperation. If the opportunity becomes available to participate in Mars exploration, interest is likely to emerge on the part of a number of other countries, such as Japan and Canada. The Space Studies Board's Committee on Cooperative Mars Exploration and Sample Return was asked by the National Aeronautics and Space Administration (NASA) to examine and report on the question of how Mars sample return missions might best be structured for effective implementation by NASA along with international partners. The committee examined alternatives ranging from scientific missions in which the United States would take a substantial lead, with international participation playing only an ancillary role, to missions in which international cooperation would be a basic part of the approach, with the international partners taking on comparably large mission responsibilities. On the basis of scientific strategies developed earlier by the Space Studies Board, the committee considered the scientific and technical basis of such collaboration and the most mutually beneficial arrangements for constructing successful cooperative missions, particularly with the USSR

    Genetic Susceptibility of Cultured Shrimp (\u3ci\u3ePenaeus vannamei\u3c/i\u3e) to Infectious Hypodermal and Hematopoietic Necrosis Virus and \u3ci\u3eBaculovirus penaei\u3c/i\u3e: Possible Relationship with Growth Status and Metabolic Gene Expression

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    Offspring of four crosses (I, II, III, and IV) of Penaeus vannamei from known high- and low-growth families were challenged with infectious hypodermal and hematopoietic necrosis virus (IHHNV) and Baculovirus penaei (BP) to compare their susceptibility to these viral agents and examine the genetic component involved in disease resistance or susceptibility. Family crosses were made using broodstock from five families developed by the U.S. Marine Shrimp Farming Program. The prevalence of IHHNV infection was highest in cross I and lowest in cross III. Cross I was developed using male and female broodstock from the low-growth family 1.6, and cross III was developed using a female from the high-growth family 1.3 and a male from the low-growth family 1.6. The prevalence of BP infection at Day 4 was highest (100%) in cross IV, which was developed using a female from the low-growth family 1.4 and a male from the high-growth family 1.5. The reciprocal cross, cross III, had the lowest (68%) prevalence at Day 4 postexposure. Both crosses I and II had 88% prevalence of infection at Day 4. Despite 100% prevalence of BP infection in cross IV at 4 days, animals from this cross and cross II exhibited high survival by Day 18 (85 and 77%). On the other hand, crosses I and III (with 88 and 68% prevalence at Day 4, respectively) showed low survival at Day 18 (19 and 24%). On the basis of prevalence of infection and mortality rates, it was concluded that the susceptibility to BP in penaeid shrimp is governed by the genetic background of the parental crosses. The random amplified polymorphic DNA polymorphisms for crosses I, II, III, and IV, were 43, 45, 53, and 51%, respectively, showing no clear relationship between IHHNV and BP prevalence of infection and levels of nuclear genetic diversity. Though the mtDNA haplotypes in offspring from the different crosses were the same, major differences were observed in both steady-state levels and patterns of expression of the mitochondrial 12s rRNA in offspring obtained at various early developmental stages from each of the four crosses. The possible relationship among disease susceptibility, growth status, and expression of mitochondrial 12s rRNA is discussed in the context of a complex nuclear-cytoplasmic genetic system involved in the regulation of gene expression

    Determinants of Symptomatic Vulvovaginal Candidiasis among Human Immunodeficiency Virus Type 1 Infected Women in Rural KwaZulu-Natal, South Africa

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    Introduction. We sought to determine the association between HIV-induced immunosuppression, virologic correlates, and vulvovaginal candidiasis (VVC). Methods. This is a retrospective cohort study, where HIV infected and uninfected women were studied with VVC being the primary outcome. Ninety-seven HIV-infected and 101 HIV-uninfected women were enrolled between June and December 2011. Cases of VVC were confirmed. HIV RNA load was determined by RT-PCR and CD4 counts were obtained from medical records. Results. Fifty-two of 97 (53.6%) HIV-infected and 38/101 (37.6%) HIV-uninfected women were diagnosed with VVC (P = 0.032). The relative risk for VVC amongst HIV-infected patients was 1.53 (95% CI: 1.04–2 P = 0.024). Cases of VVC increased at CD4+ T cell count below 200 cells/mm3 (P \u3c 0.0001) and plasma HIV RNA load above 10 000 copies/mL (P \u3c 0.0001). VVC was associated with increased genital shedding of HIV (P = 0.002), and there was a linear correlation between plasma HIV load and genital HIV shedding (r = 0.540; R2 = 0.292; P \u3c 0.0001). Women on HAART were 4-fold less likely (P = 0.029) to develop VVC. Conclusion. CD4 counts below 200 cells/mm3 and plasma HIV loads ≥10 000 copies/mL were significantly associated with VVC

    Association between symptomatic vulvovaginal candidiasis and HIV RNA levels in plasma and genital secretions among women on HAART

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    Background. Genital tract (GT) inflammation plays a major role in HIV transmission. We aimed to determine the association between symptomatic vulvovaginal candidiasis (VVC) and HIV RNA levels in plasma and GTs of HIV-infected women on highly active antiretroviral therapy (HAART). Method. Women with VVC on HAART were recruited from a primary healthcare clinic in KwaZulu-Natal Province, South Africa, between June 2011 and December 2011. VVC was diagnosed clinically, supported by Gram staining and culture of genital secretions. HIV RNA load was determined by reverse transcription polymerase chain reaction. CD4+ counts were obtained from patients’ medical records. Results. Plasma HIV RNA was detected in 42 of 60 (70%) patients on HAART. The mean duration (± standard deviation) on HAART for these patients was 4.2 (±1.6) months v. 10.7 (±1.4) months for the remaining 18 patients (p10 cells/5 high microscopic fields (p=0.007). Conclusion. Given that the majority of women had recently initiated HAART (allowing a high rate of detectable plasma HIV RNA), there was insufficient evidence to conclude that VVC was predictive of high plasma HIV RNA levels. It is more likely that this cohort of immunosuppressed women were prone to develop VVC. Plasma HIV loads and local genital inflammation were predictors of genital HIV detectability

    Expression of toll-like receptor (TLR)-2 and TLR4 in monocytes following stimulations by genital secretions of HIV infected and uninfected women with symptomatic vulvo-vaginal candidiasis

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    Vulvo-vaginal candidiasis (VVC) is a common condition in human immunodeficiency virus (HIV)- infected women. Toll-like receptor (TLR) 2 and TLR4 are key pattern-recognition receptors of the innate immune system in sensing Candida albicans. The aim of this study was to assess the expression of TLR2 and TLR4 signaling pathways in HIV-infected and uninfected women with VVC. Cervico-vaginal fluids (CVF) were obtained from 7 HIV infected and 11 HIV uninfected clinic attendees in KwaZulu-Natal between June, 2011 and December, 2011. VVC was diagnosed clinically and confirmed by Gram stain and culture of genital samples. Monocytes were isolated from a healthy adult volunteer, pre-incubated with anti-TLR2, anti-TLR4 and a combination of anti-TLR2/anti-TLR4 monoclonal antibodies. Monocytes were then stimulated by CVF. Levels of cytokines were measured by Luminex® multiplex immunoassays. Compared with baseline concentrations, stimulation with CVF of HIV+VVC+ women post-TLR2 blockage increased IL-6, IL-10 and IL-13 production by 165.5, 162.5 and 106.7%, respectively. Using paired T-tests, there was a significant difference in the increase of the concentrations of IL-6 (P = 0.04), IL-10 (P = 0.003), and IL-13 (P = 0.031) when comparing stimulation by CVF of HIV+VVC+ versus stimulation by CVF of HIV-VVC+ patients. There was a linear correlation between genital HIV RNA loads and mean level production of IL-6 (r = 0.722; R2 = 0.679; P = 0.067) as well as IL-8 (r = 0.910; R2 = 0.833; P = 0.004). Findings suggest potential roles of TLR2 in the pathogenesis of VVC among HIV-infected women

    Ernst Freund as Precursor of the Rational Study of Corporate Law

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    Gindis, David, Ernst Freund as Precursor of the Rational Study of Corporate Law (October 27, 2017). Journal of Institutional Economics, Forthcoming. Available at SSRN: https://ssrn.com/abstract=2905547, doi: https://dx.doi.org/10.2139/ssrn.2905547The rise of large business corporations in the late 19th century compelled many American observers to admit that the nature of the corporation had yet to be understood. Published in this context, Ernst Freund's little-known The Legal Nature of Corporations (1897) was an original attempt to come to terms with a new legal and economic reality. But it can also be described, to paraphrase Oliver Wendell Holmes, as the earliest example of the rational study of corporate law. The paper shows that Freund had the intuitions of an institutional economist, and engaged in what today would be called comparative institutional analysis. Remarkably, his argument that the corporate form secures property against insider defection and against outsiders anticipated recent work on entity shielding and capital lock-in, and can be read as an early contribution to what today would be called the theory of the firm.Peer reviewe

    Meaning behind measurement : self-comparisons affect responses to health related quality of life questionnaires

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    Purpose The subjective nature of quality of life is particularly pertinent to the domain of health-related quality of life (HRQOL) research. The extent to which participants’ responses are affected by subjective information and personal reference frames is unknown. This study investigated how an elderly population living with a chronic metabolic bone disorder evaluated self-reported quality of life. Methods Participants (n = 1,331) in a multi-centre randomised controlled trial for the treatment of Paget’s disease completed annual HRQOL questionnaires, including the SF-36, EQ-5D and HAQ. Supplementary questions were added to reveal implicit reference frames used when making HRQOL evaluations. Twenty-one participants (11 male, 10 female, aged 59–91 years) were interviewed retrospectively about their responses to the supplementary questions, using cognitive interviewing techniques and semi-structured topic guides. Results The interviews revealed that participants used complex and interconnected reference frames to promote response shift when making quality of life evaluations. The choice of reference frame often reflected external factors unrelated to individual health. Many participants also stated that they were unclear whether to report general or disease-related HRQOL. Conclusions It is important, especially in clinical trials, to provide instructions clarifying whether ‘quality of life’ refers to disease-related HRQOL. Information on selfcomparison reference frames is necessary for the interpretation of responses to questions about HRQOL.The Chief Scientist Office of the Scottish Government Health Directorates, The PRISM funding bodies (the Arthritis Research Campaign, the National Association for the Relief of Paget’s disease and the Alliance for Better Bone Health)Peer reviewedAuthor final versio
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